There are known playback devices designed as compact disc players in which a reader device reads out digital audio data from data tracks on a compact disc. These data tracks are arranged concentrically with an axis of rotation of the compact disc, and, to simplify the following description, they approximate a single spiral data track arranged on the compact disc. For readout of digital audio data stored in data tracks, the compact disc is rotated on a turntable, and the reader device moves radially with respect to the axis of rotation over the compact disc to read out the digital audio data.
Drives of compact disc players designed in this way are usually operated in an operating mode with a constant linear speed. Depending on the position of the reader device on the compact disc, the rotational speed is regulated so that a continuous data stream is read out at a constant amount of data per unit of time, i.e., at a constant linear speed. The constant linear speed is limited in particular by the tracking of the reader device over data tracks of the compact disc and by the processing capacity of the playback device for analysis of the digital audio data read out from the data tracks on the compact disc.
In the case of jumping tracks in the constant linear speed operating mode, the rotational speed must be adjusted as a function of the position of the reader device in order to maintain a constant amount of data per unit of time in reading out the digital audio data from the data tracks of the compact disc. However, the rate of access to data in the case of jumping tracks is reduced by the time required for adjustment of the rotational speed.
The method according to the present invention has the advantage over the related art that the rotational speed in playing back the disc-shaped storage medium is kept constant. In this way, the playback device is operated in a constant angular speed operating mode. In jumping tracks in the constant angular speed operating mode, it is not necessary to adjust rotational speed to control the amount of data read out per unit of time so that a higher access rate to data in the data tracks can be achieved when jumping tracks.
Another advantage is that an outermost data track of the disc-shaped storage medium which is opposite the axis of rotation and has been written with useful data is determined; a value is obtained for the amount of data stored in the outermost data track; the rotational speed is adjusted as a function of the amount of data thus determined and a data transfer rate, the data transfer rate indicating a maximum amount of data that can be read out by the playback device per unit of time, so that the useful data stored in the outermost data track can be read out at the data transfer rate when playing back the disc-shaped storage medium. In this way, the rotational speed of the respective disc-shaped storage medium is adjusted as a function of the data structure stored on the storage medium or the arrangement of data tracks having useful data on the storage medium. Thus, the rotational speed for each storage medium can be adjusted so that the maximum possible amount of data read out for this storage medium can be utilized per unit of time as a function of the data structure stored on the respective storage medium.
An especially simple method of determining the outermost data track is by analysis of content data in a lead-in area of the disc-shaped storage medium.
An especially accurate method of determining the value for the amount of data stored in the outermost data track is obtained by track jumping by the reader device of the playback device to this data track, by reading out the useful data from this data track and by measuring the number of useful data bits of this data track read out or by measuring the time required for this readout operation at a given constant linear speed in data readout.